Platinum Acetylide Research Articles

Boosting the Adhesivity of π-Conjugated Polymers by Embedding Platinum Acetylides towards High-Performance Thermoelectric Composites.

Single-walled carbon nanotubes (SWCNTs) incorporated with π-conjugated polymers, have proven to be an effective approach in the production of advanced thermoelectric composites. However, the studied polymers are mainly limited to scanty conventional conductive polymers, and their performances still remain to be improved. Herein, a new planar moiety of platinum acetylide in the π-conjugated system is introduced to enhance the intermolecular interaction with the SWCNTs via π–π and d–π interactions, which is crucial in regulating the thermoelectric performances of SWCNT-based composites. As expected, SWCNT composites based on the platinum acetylides embedded polymers displayed a higher power factor (130.7 ± 3.8 μW·m−1·K−2) at ambient temperature than those without platinum acetylides (59.5 ± 0.7 μW·m−1·K−2) under the same conditions. Moreover, the strong interactions between the platinum acetylide-based polymers and the SWCNTs are confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) measurements.

Facile Synthesis of Luminescent Ir-Pt-Ir Trimetallic Complexes.

A new class of luminescent, heterotrimetallic supramolecular constructs partnering two bis-cyclometalated iridium centers with a diimine platinum acetylide center is introduced. Whereas most supramolecular constructs featuring cyclometalated iridium involve elaborate bridging ligands and are prepared under forcing conditions with low to moderate yields, the three Ir-Pt-Ir complexes described here are prepared at room temperature from simple precursors and isolated in near-quantitative yields. ESI-MS, NMR spectroscopy, and diffusion ordered spectroscopy confirm the identity and homogeneity of the trimetallic products. In comparison with monometallic model complexes, analysis of UV/Vis absorption, steady-state photoluminescence and time-resolved emission reveals the impacts of supramolecular assembly on the photophysical properties. UV/Vis absorption and cyclic voltammetry suggest perturbation of some frontier orbital energies as a result of assembly, and the emission spectra and lifetimes reveal efficient excited-state energy transfer via a Dexter mechanism, and show that the site of luminescence (platinum or iridium) depends on the identity of the cyclometalating ligand bound to iridium.

Triplet state structure-property relationships in a series of platinum acetylides: effect of chromophore length and end cap electronic properties.

To develop quantitative structure-spectroscopic property relationships in platinum acetylides, we investigated the triplet state behavior of nominally centrosymmetric chromophores trans-Pt(PBu3)2(C[triple bond, length as m-dash]C-Phenyl-X)2, where X = diphenylamino, NH2, OCH3, t-Bu, CH3, H, F, benzothiazole, CF3, CN, and NO2. We measured ground state absorption, phosphorescence, excitation and triplet state absorption spectra and triplet lifetimes. By DFT we calculated the phosphorescence emission energy (ET), the spin density on the end cap (SD(X)), triplet state geometry and the distance between the triplet centroid and the central platinum atom (RS-Pt(X)). Compounds with electron-donating X have smaller triplet state lifetime, blue-shifted phosphorescence and larger triplet potential energy surface displacement associated with the C[triple bond, length as m-dash]C bond. Compounds with electron-withdrawing X have larger triplet lifetime, red-shifted phosphorescence and smaller triplet potential energy surface displacement associated with the C[triple bond, length as m-dash]C bond. The range of spin-orbit-coupling between the platinum atom and the triplet centroid was determined to be 6 Å. The quantity RS-Pt is shown to be a linear function of one-dimensional well length calculated from experimental ET. The multiple examples demonstrate RS-Pt is a useful descriptor for analyzing triplet state behavior.

Supramolecular Transformation of Metallacycle-linked Star Polymers Driven by Simple Phosphine Ligand-Exchange Reaction.

As a common phenomenon in biological systems, supramolecular transformations of biomacromolecules lead to specific biological functions as outputs, which thus inspire people to construct biomimetic dynamic systems through supramolecular transformation strategy. It should be noted that well-modulating the artificial macromolecules to fine-tune their properties is of great significance yet still remains a big challenge in polymer chemistry. In this study, through the combination of coordination-driven self-assembly and postassembly ring-opening polymerization, a six-armed star polymer linked by well-defined hexagonal metallacycle as core was successfully prepared. At the same time, the trans-platinum acetylide moieties as transformation sites were anchored onto the discrete metallacycle scaffold. Subsequently, the simple phosphine ligand-exchange reaction induced the conversions of platinum acetylide building blocks with the varied binding angles, which thus resulted in the successive hexagon-rhomboid-hexagon transformations of metallacyclic scaffold, therefore allowing for the corresponding supramolecular transformation of metallacycle-linked star polymers. More importantly, accompanied by such transformation process, property modulation of the resultant polymers has been successfully realized. In a word, by taking advantage of dynamic nature of metal-ligand coordination bonds and simple phosphine ligand-exchange reactions, facile architecture transformation of a star polymer to a linear polymer and back to a star polymer was successfully realized, which may provide a promising approach toward the construction of new dynamic polymeric materials.

Directional Self-Sorting with Cucurbit[8]uril Controlled by Allosteric π-π and Metal-Metal Interactions.

To maximize Coulombic interactions, cucurbit[8]uril (CB[8]) typically forms ternary complexes that distribute the positive charges of the pair of guests (if any) over both carbonylated portals of the macrocycle. We present here the first exception to this recognition pattern. Platinum(II) acetylides flanked by 4'-substituted terpyridyl ligands (tpy) form 2:1 complexes with CB[8] in an exclusively stacked head-to-head orientation in a water/acetonitrile mixture. The host encapsulates the pair of tpy substituents, and both positive Pt centers sit on top of each other at the same CB[8] rim, leaving the other rim free of any interaction with the guests. This dramatic charge imbalance between the CB[8] rims would be electrostatically penalizing, were it not for allosteric π-π interactions between the stacked tpy ligands, and possible metal-metal interactions between both Pt centers. When both tpy and acetylides are substituted with aryl units, the metal-ligand complexes form 2:2 assemblies with CB[8] in aqueous medium, and the directionality of the assembly (head-to-head or head-to-tail) can be controlled, both kinetically and thermodynamically.

Poly(arylene ether)s based on platinum(ii) acetylide complexes: synthesis and photophysical and nonlinear absorption properties

Poly(arylene ether)s based on Pt(ii) acetylide and solid-state bulky materials with trade-offs between strong RSA and good transparency were reported.

Metallo-supramolecular polymers derived from benzothiadiazole-based platinum acetylide complexes for fluorescent security application.

Metallo-supramolecular polymers with the incorporation of benzothiadiazole-substituted organoplatinum moiety have been successfully constructed. The designed monomer displays intense fluorescence signals, which are severely quenched upon the supramolecular polymerization process. On–off switching of fluorescence can be further exploited for data security materials in response to the chemical stimuli. Accordingly, the resulting supramolecular polymers can be regarded as a novel and efficient candidate toward information processing applications.

Facile construction of organometallic rotaxane-terminated dendrimers using neutral platinum-acetylides as the main scaffold.

We present the successful construction of a new family of organometallic rotaxane-terminated dendrimers using neutral platinum-acetylides as the main scaffold. The fourth generation dendrimer has 24 rotaxane moieties on the surface termini in a monodisperse manner.

In Search of Deeper Blues: Trans-N-Heterocyclic Carbene Platinum Phenylacetylide as a Dopant for Phosphorescent OLEDs.

A trans-N-heterocyclic carbene (NHC) platinum(II) acetylide complex bearing phenyl acetylene ligands (NPtPE1) has been synthesized via the Hagihara reaction in 64% yield. The complex features spectrally narrow deep blue emission with a phosphorescence quantum yield (0.30) and lifetime (∼10 μs) in the solid state. The modest quantum yield and lifetime make NPtPE1 a candidate for incorporation into an organic light emitting diode (OLED). Prototype devices exhibited a maximum EQE of 8% with CIE (0.20,0.20). To the best of our knowledge, this is the first example of a platinum(II) acetylide bearing NHC ligands to be incorporated into an OLED.

Near-IR electrochromism of the electropolymerization film prepared from a cyclometalated dinuclear Pt(II) complex

The cyclometalated dinuclear platinum acetylide with a 9,9-dioctylfluorene spacer and two terminal triphenylamine groups has been successfully synthesized and characterized by 1H NMR, 13C NMR and MALDI-TOF MS. The active triphenylamine groups efficiently trigger the oxidative electropolymerization process to form a reddish-orange film on the working Pt and ITO electrodes by cyclic voltammetry. The compact film shows a polyaniline-like AC impedance behavior and an inverse dependence of AC impedance on its thickness. As a result of switching of the MLCT/ICT and dication absorption transitions between 0 and +1.8 V, this metallopolymer film exhibits the near-IR electrochromism with significant optical contrast ratio (ΔT%=78.3% at λ=775nm), comparative response time (3.8s for the coloration step and 11.0s for the bleaching step) and high anodic coloration efficiency (CE=208.3C−1·cm2).

Mechanical Activation of Platinum-Acetylide Complex for Olefin Hydrosilylation.

Harnessing mechanical forces to activate latent catalysts has emerged as a novel approach to control the catalytic reactions in organic syntheses and polymerization processes. However, using polymer mechanochemistry to activate platinum-based catalysts, a class of important organometallic catalysts in industry, has not been demonstrated so far. Here we show that the platinum-acetylide complex is mechanoresponsive and can be incorporated into a polymer backbone to form a new mechanophore. The mechanically induced chain scission was demonstrated to be able to release catalytically active platinum species which could catalyze the olefin hydrosilylation process. Various control experiments were conducted to confirm that the chain scission and catalytic reaction were originated from the ultrasound-induced dissociation of platinum-acetylide complex. This work further exemplifies the utilization of organometallic complexes in design and synthesis of latent catalysts for mechanocatalysis and development of self-healing materials based on silicone polymers.

Cooperative Supramolecular Polymerization of Fluorescent Platinum Acetylides for Optical Waveguide Applications.

One-dimensional organic structures with well-oriented π-aggregation, strong emission, and ease of processability are desirable for optoelectronic waveguiding devices. Herein, a strategy is developed to attain this objective by self-assembling platinum(II) acetylides into fluorescent supramolecular polymers via cooperative mechanism. The resulting high-molecular-weight supramolecular polymers are capable of forming electrospun microfibers with uniform geometry and smooth surface, which enable light propagation with extremely low scattering loss (0.008 dB μm-1 ). With the elaborate combination of bottom-up supramolecular polymerization and top-down electrospinning techniques, this work offers a novel and versatile avenue toward high-performance optical waveguiding materials.

Cooperative Supramolecular Polymerization of Fluorescent Platinum Acetylides for Optical Waveguide Applications

AbstractOne‐dimensional organic structures with well‐oriented π‐aggregation, strong emission, and ease of processability are desirable for optoelectronic waveguiding devices. Herein, a strategy is developed to attain this objective by self‐assembling platinum(II) acetylides into fluorescent supramolecular polymers via cooperative mechanism. The resulting high‐molecular‐weight supramolecular polymers are capable of forming electrospun microfibers with uniform geometry and smooth surface, which enable light propagation with extremely low scattering loss (0.008 dB μm−1). With the elaborate combination of bottom‐up supramolecular polymerization and top‐down electrospinning techniques, this work offers a novel and versatile avenue toward high‐performance optical waveguiding materials.

Two-Photon Spectroscopy of a Series of Platinum Acetylides: Conformation-Induced Ground-State Symmetry Breaking.

With the goal of elucidating electronic and conformational effects on structure-spectroscopic property relationships in platinum acetylides, we synthesized a series of nominally centrosymmetric chromophores trans-Pt(PBu3)2(C≡C-Phenyl-X)2, where X = diphenylamino (DPA), NH2, OCH3, t-Bu, CH3, H, F, benzothiazole (BTH), CF3, CN, and NO2. We collected one- and two-photon absorption spectra and also performed density functional theory (DFT) and time-dependent (TD) DFT calculations on the ground- and excited-state properties of these compounds. The DFT calculations revealed facile rotation between the two ligands, suggesting that the compounds exhibit nonplanar ground-state conformations in solution. TDDFT calculation of the S1 state energy and transition dipole moment for a nonplanar conformation gave good agreement with experiment. Two-photon absorption spectra obtained from these compounds allowed estimation of the change of permanent electric dipole moment upon vertical excitation from ground state to S1 state. The values are small Δμ < 1.0 D for neutral substituents such as CH3, H, and F but increase sharply to Δμ ≈ 11 D for electron-accepting NO2. When in a nonplanar conformation, the corresponding calculated Δμ values showed good agreement with the experimental data indicating that the two-photon spectra result from nonplanar ground-state conformations. Previously studied related chromophores having extended conjugation ( Rebane, A.; Drobizhev, M.; Makarov, N. S.; Wicks, G.; Wnuk, P.; Stepanenko, Y.; Haley, J. E.; Krein, D. M.; Fore, J. L.; Burke, A. R.; Slagle, J. E.; McLean, D. G.; Cooper, T. M. J. Phys. Chem. A 2014 , 118 , 3749 - 3759 ) show similar dependence of Δμ on the substituents, which allows us to conclude that the excited-state properties of these floppy chromophores are a function of the electronic properties of the substituents, ligand size, and nonplanar molecular conformation.

Efficient reverse saturable absorption of sol-gel hybrid plasmonic glasses

Monolithic silica sol-gel glasses doped with platinum(II) acetylide complexes possessing respectively four or six phenylacetylene units (PE2-CH2OH and PE3-CH2OH) in combination with various concentrations of spherical and bipyramidal gold nanoparticles (AuNPs) known to enhance non-linear optical absorption, were prepared and polished to high optical quality. The non-linear absorption of the glasses was measured and compared to glasses doped solely with AuNPs, a platinum(II) acetylide with shorter delocalized structure, or combinations of both. At 532 nm excitation wavelength the chromophore inhibited the non-linear scattering previously found for glasses only doped with AuNPs. The measured non-linear absorption was attributed to reverse saturable absorption from the chromophore, as previously reported for PE2-CH2OH/AuNP glasses. At 600 nm strong nonlinear absorption was observed for the PE3-CH2OH/AuNPs glasses, also attributed to reverse saturable absorption. But contrary to previous findings for PE2-CH2OH/AuNPs, no distinct enhancement of the non-linear absorption for PE3-CH2OH/AuNPs was observed. A numerical population model for PE3-CH2OH was used to give a qualitative explanation of this difference. A stronger linear absorption in PE3-CH2OH would cause the highly absorbing triplet state to populate quicker during the leading edge of the laser pulse and this would in turn reduce the influence from two-photon absorption enhancement from AuNPs.

Platinum(ii) acetylide complexes with star- and V-shaped configurations possessing good trade-off between optical transparency and optical power limiting performance

Two series of Pt(ii) acetylide complexes containing dimesitylborane and phenyl terminal groups with star- and V-shaped configurations were synthesized.

Theoretical Studies on One-Photon and Two-Photon Absorption Properties of Platinum Acetylide Complexes

Theoretical Studies on One-Photon and Two-Photon Absorption Properties of Platinum Acetylide Complexes

Cyclometalated NCN platinum(II) acetylide complexes – Synthesis, photophysics and OLEDs fabrication

The novel cyclometalated NCN platinum(II) acetylide complexes were synthesized. As precursors of acetylide ligands were used 9,9-dibutyl-2-ethynylfluorene, 9-butyl-3-ethynylcarbazole, and 5-ethynyl-2,2′-bithiophene, whereas 1,3-di(2-pirydyl)benzene derivatives were cyclometalating NCN ligands. Variable character of ligands allowed to prepare a series of novel platinum(II) complexes, which showed light emission in a wide wavelength range from 410 to 625 nm. The optical and electrochemical properties of new complexes were examined and compared with theoretical DFT calculations. Complexes containing fluorenyl and carbazyl motif were used as emitters in an organic light-emitting diodes. The applicability of these Pt(II) complexes for electroluminescence was examined.

Enhancement of Carrier Mobility through Deformation Potential in Metal-Containing Insulated Molecular Wires

We used first-principles calculations to investigate the hole mobility of metal-containing poly(phenylene ethynylene) insulated molecular wires. The metal–organic bond effects were considered using ruthenium(II) porphyrin–pyridyl and platinum(II) acetylide as the organometallic moieties. We found that high hole mobility can be achieved even when the metal–organic dπ–pπ interaction is weak. The weak metal–organic interaction reduces the structural deformation that accompanies hole hopping and compensates the reduced conjugation inside the molecular wire. Our results suggest a new principle for the design of functionalized metallopolymers with high carrier mobilities.

ChemInform Abstract: Heavy Metal Complex Containing Organic/Polymer Materials for Bulk‐Heterojunction Photovoltaic Devices

AbstractReview: 113 refs.